The present invention relates generally to an automatic meter reading system. In particular, the invention relates to a system which uses radio frequency (RF) transmitters to send encoded meter readings to a receiver which is able to collect data from a plurality of such devices.
In an automatic meter reading system, of the type used to read utility meters, it is desirable to have a system in which a meter reader can periodically pass through an area containing a number of meters and collect their data. In the past, systems have existed in which the meters included transponder-like systems. In a typical system known in the prior art, a mobile collector unit, such as a van, would traverse an area collecting data from encoder/receiver/transmitter ("ERT") unit. The ERT units contained an encoder, a receiver, and a transmitter. The radio mounted in the van would transmit a "wake-up" signal which served to cause the ERT units in its proximity to send out their encoded data. Such a system, due to its inclusion of both a transmitter and a receiver, is called a "two-way" system.
As will be understood by those skilled in the art, a simpler, and, thus, less expensive system, in which only the encoder and transmitter were located at the site being monitored would be desireable to minimize costs. However, such a "one-way" system would have to conserve battery power, prevent conflicts in transmissions, and have a receiver/collector unit to identify valid transmissions from identifiable locations.